Mounsey died of cancer on Saturday at her Los Angeles home, said her daughter, Allegra Clegg of Los Angeles.

Mounsey danced with the City Ballet from 1948 to 1958, rising from soloist to principal dancer.

She was the Dark Angel in Balanchine’s “Serenade” and Siren in his 1950 revival of “Prodigal Son,” which were among her favorite roles, her daughter said.

For Robbins, she originated the roles of the Queen in “The Cage,” the Harp in “Fanfare” and the Wife in “The Concert.”

Mounsey was born Yvonne Louise Leibbrandt in 1919 on a South African dairy farm outside of Pretoria. She began taking ballet lessons at 7 with a former member of Russian ballerina Anna Pavlova’s company.

She later studied and danced in England and performed around the world with various companies, including the famed Ballet Russe de Monte Carlo.

She was with another company, the Original Ballet Russe, when Balanchine saw her in New York in 1940. He created a part for her in his 1941 “Balustrade.”

She became stranded in Cuba in 1941 when the other dancers on tour went on strike and the company disbanded. She survived by becoming a successful nightclub dancer.

“She walked into one of the fanciest nightclubs … and got a job and stayed there for a year,” her daughter said. “She was so resourceful. She came from a farm, a very poor upbringing and it was like, `OK, I’m here in Cuba and I have no resources. What do I do?’ “

After her New York City Ballet years, she helped co-found a ballet company in her native South Africa.

In 1966, Mounsey moved to Los Angeles and opened the Westside School of Ballet, teaching the neoclassical Balanchine technique, which has become a signature style of ballet in America. The Santa Monica school became influential and its students have included former City Ballet star Jock Soto and current company principal dancers Andrew Veyette and Tiler Peck. The school also counts Joy Womack, the first American woman to dance with the Bolshoi Ballet, among the world-class dancers it has trained.

“She just had this love and passion for ballet that exuded from her,” she said. “She just wanted you to enjoy dancing and enjoy that art form, because 98 percent of her students would never become professional ballet dancers.”

Mounsey stressed passion and discipline in art and life, her daughter said.

“`Whatever you do,’ she would say to you, `Do it 110 percent, whether you’re the housekeeper or the bus driver or a doctor.’”

Mounsey was married three times, to Duncan Mounsey, Albert Hall Hughey and Kelvin Clegg. In addition to her daughter, she is survived by two stepsons, a grandson and a sister.